This invention relates to resistors used in the dynamic braking function of electric traction motors such as those found in railroad locomotives, and in particular to an improved resistive ribbon element of the resistor which reduces the pressure drop of air passing through the resistor but maintains a predetermined column load strength for the ribbon element.
Resistors of the aforementioned type are well known. One example of such resistor is shown in Kuhn et al U.S. Pat. No. 2,680,178. The reflexed resistance ribbon of that patent has a transverse cross section comprising a triple convolution to provide the desired column load strength for the lengths between the reflexes and a resistance to airflow passing through the resistor for maximizing the heat transfer. Another example of a dynamic braking locomotive resistor is disclosed in Luy U.S. Pat. No. 4,316,172. As shown therein, reflexed resistance ribbons of the type shown in Kuhn et al U.S. Pat. No. 2,680,178 are supported between insulators within a frame by mounting brackets which attach to the insulators and support the reflexes of the resistance ribbon away from the surface of the insulator. This patent also shows a plurality of such reflexed resistance ribbons supported in immediately adjacent side-by-side juxtaposition by a common mounting bracket.
The resistor comprised of a single supporting frame structure is known as a resistor bank. In diesel electric locomotives and other vehicular traction applications, several resistor banks are commonly stacked in a serial arrangement in a forced ventilation system to dissipate the power generated by the drive motor in a braking situation. It has been found in some applications employing multiple resistor banks that the pressure drop across the combined resistor banks is too great, creating a detrimental resistance to airflow therethrough and thereby reducing the heat transfer cooling effect sought for the resistors. In extreme cases the pressure drop can be so great as to cause stalling of the air flow through the fan and resistor banks.